It was an interesting study but it was criticized in the scientific community. Well, he did another study in 2009 and this time was more rigorous. The follow up study is called The Chronic Dependence of Popular Religiosity upon Dysfunctional Psychosociological Conditions. Now I haven't read the whole thing, but Tom Rees of Epiphenom has. He was attracted to the charts, as I was, which I've added below.
What societal ills bring a country down from being successful and healthy? Paul used indicators like murder, suicide rates, size of prison populations, mortality, alcohol consumption, poverty, unemployment, sexually transmitted diseases, abortions and deaths. I think he had some positive indicators like marriages too.
Results? Unhealthy societies are more religious. Religion needs a dysfunctional society to flourish, which explains why a first world country like the U.S. can still be so religious, as you can see in all the charts. (click for larger versions)
Tom Rees also did a paper called Is Personal Insecurity a Cause of Cross-National Differences in the Intensity of Religious Belief? In it Rees found that the more insecure a society and its people are, the more religious that society is. So these two studies support each other. You can see his review of his own study at his blog, Epiphenom. It's got all his nice graphs there, easy to read.
Here is a video of Gregory Paul talking about his work. It's hard to hear him clearly, but I watched some of it and he said the way to help the U.S. become more secular was to get universal healthcare. The talk was in 2008, by the way, so maybe we'll see if our recent pathetic bill will make a difference in the religiosity of America.
So making society more stable and helping people to feel more secure would help to get them out from under the boot heel of religion? Sounds plausible. I'd like to see more work done. How would you test that hypothesis? If you could choose 2 changes made to your country to make it more stable and less religious, what would you pick?